// Allocators -*- C++ -*-                                                      
                                                                               
// Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.         
//                                                                             
// This file is part of the GNU ISO C++ Library.  This library is free         
// software; you can redistribute it and/or modify it under the                
// terms of the GNU General Public License as published by the                 
// Free Software Foundation; either version 2, or (at your option)             
// any later version.                                                          
                                                                               
// This library is distributed in the hope that it will be useful,             
// but WITHOUT ANY WARRANTY; without even the implied warranty of              
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               
// GNU General Public License for more details.                                
                                                                               
// You should have received a copy of the GNU General Public License along     
// with this library; see the file COPYING.  If not, write to the Free         
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,    
// USA.                                                                        
                                                                               
// As a special exception, you may use this file as part of a free software    
// library without restriction.  Specifically, if other files instantiate      
// templates or use macros or inline functions from this file, or you compile  
// this file and link it with other files to produce an executable, this       
// file does not by itself cause the resulting executable to be covered by     
// the GNU General Public License.  This exception does not however            
// invalidate any other reasons why the executable file might be covered by    
// the GNU General Public License.                                             
                                                                               
/*                                                                             
 * Copyright (c) 1996-1997                                                     
 * Silicon Graphics Computer Systems, Inc.                                     
 *                                                                             
 * Permission to use, copy, modify, distribute and sell this software          
 * and its documentation for any purpose is hereby granted without fee,        
 * provided that the above copyright notice appear in all copies and           
 * that both that copyright notice and this permission notice appear           
 * in supporting documentation.  Silicon Graphics makes no                     
 * representations about the suitability of this software for any              
 * purpose.  It is provided "as is" without express or implied warranty.       
 */                                                                            
                                                                               
/** @file ext/pool_allocator.h                                                 
 *  This file is a GNU extension to the Standard C++ Library.                  
 *  You should only include this header if you are using GCC 3 or later.       
 */                                                                            
#ifndef _POOL_ALLOCATOR_H                                                      
#define _POOL_ALLOCATOR_H 1                                                    
                                                                               
#include <bits/c++config.h>                                                    
#include <cstdlib>                                                             
#include <new>                                                                 
#include <bits/functexcept.h>                                                  
#include <bits/atomicity.h>                                                    
#include <bits/concurrence.h>                                                  
                                                                               
namespace __gnu_cxx                                                            
{                                                                              
  /**                                                                          
   *  @if maint                                                                
   *  Uses various allocators to fulfill underlying requests (and makes as     
   *  few requests as possible when in default high-speed pool mode).          
   *                                                                           
   *  Important implementation properties:                                     
   *  0. If globally mandated, then allocate objects from new                  
   *  1. If the clients request an object of size > _S_max_bytes, the resulting
   *     object will be obtained directly from new                             
   *  2. In all other cases, we allocate an object of size exactly             
   *     _S_round_up(requested_size).  Thus the client has enough size         
   *     information that we can return the object to the proper free list     
   *     without permanently losing part of the object.                        
   *                                                                           
   *  @endif                                                                   
   *  (See @link Allocators allocators info @endlink for more.)                
   */                                                                          
    class __pool_alloc_base                                                    
    {                                                                          
    protected:                                                                 
                                                                               
      enum { _S_align = 8 };                                                   
      enum { _S_max_bytes = 128 };                                             
      enum { _S_free_list_size = _S_max_bytes / _S_align };                    
                                                                               
      union _Obj                                                               
      {                                                                        
    union _Obj* _M_free_list_link;                                             
    char        _M_client_data[1];    // The client sees this.                 
      };                                                                       
                                                                               
      static _Obj* volatile         _S_free_list[_S_free_list_size];           
                                                                               
      // Chunk allocation state.                                               
      static char*                  _S_start_free;                             
      static char*                  _S_end_free;                               
      static size_t                 _S_heap_size;                              
                                                                               
      size_t                                                                   
      _M_round_up(size_t __bytes)                                              
      { return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); } 
                                                                               
      _Obj* volatile*                                                          
      _M_get_free_list(size_t __bytes);                                        
                                                                               
      mutex_type&                                                              
      _M_get_mutex();                                                          
                                                                               
      // Returns an object of size __n, and optionally adds to size __n        
      // free list.                                                            
      void*                                                                    
      _M_refill(size_t __n);                                                   
                                                                               
      // Allocates a chunk for nobjs of size size.  nobjs may be reduced       
      // if it is inconvenient to allocate the requested number.               
      char*                                                                    
      _M_allocate_chunk(size_t __n, int& __nobjs);                             
    };                                                                         
                                                                               
                                                                               
  template<typename _Tp>                                                       
    class __pool_alloc : private __pool_alloc_base                             
    {                                                                          
    private:                                                                   
      static _Atomic_word       _S_force_new;                                  
                                                                               
    public:                                                                    
      typedef size_t     size_type;                                            
      typedef ptrdiff_t  difference_type;                                      
      typedef _Tp*       pointer;                                              
      typedef const _Tp* const_pointer;                                        
      typedef _Tp&       reference;                                            
      typedef const _Tp& const_reference;                                      
      typedef _Tp        value_type;                                           
                                                                               
      template<typename _Tp1>                                                  
        struct rebind                                                          
        { typedef __pool_alloc<_Tp1> other; };                                 
                                                                               
      __pool_alloc() throw() { }                                               
                                                                               
      __pool_alloc(const __pool_alloc&) throw() { }                            
                                                                               
      template<typename _Tp1>                                                  
        __pool_alloc(const __pool_alloc<_Tp1>&) throw() { }                    
                                                                               
      ~__pool_alloc() throw() { }                                              
                                                                               
      pointer                                                                  
      address(reference __x) const { return &__x; }                            
                                                                               
      const_pointer                                                            
      address(const_reference __x) const { return &__x; }                      
                                                                               
      size_type                                                                
      max_size() const throw()                                                 
      { return size_t(-1) / sizeof(_Tp); }                                     
                                                                               
      // _GLIBCXX_RESOLVE_LIB_DEFECTS                                          
      // 402. wrong new expression in [some_] allocator::construct             
      void                                                                     
      construct(pointer __p, const _Tp& __val)                                 
      { ::new(__p) _Tp(__val); }                                               
                                                                               
      void                                                                     
      destroy(pointer __p) { __p->~_Tp(); }                                    
                                                                               
      pointer                                                                  
      allocate(size_type __n, const void* = 0);                                
                                                                               
      void                                                                     
      deallocate(pointer __p, size_type __n);                                  
    };                                                                         
                                                                               
  template<typename _Tp>                                                       
    inline bool                                                                
    operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)             
    { return true; }                                                           
                                                                               
  template<typename _Tp>                                                       
    inline bool                                                                
    operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&)             
    { return false; }                                                          
                                                                               
  template<typename _Tp>                                                       
    _Atomic_word                                                               
    __pool_alloc<_Tp>::_S_force_new;                                           
                                                                               
  template<typename _Tp>                                                       
    _Tp*                                                                       
    __pool_alloc<_Tp>::allocate(size_type __n, const void*)                    
    {                                                                          
      pointer __ret = 0;                                                       
      if (__n)                                                                 
    {                                                                          
      if (__n <= max_size())                                                   
        {                                                                      
          // If there is a race through here, assume answer from getenv        
          // will resolve in same direction.  Inspired by techniques           
          // to efficiently support threading found in basic_string.h.         
          if (_S_force_new == 0)                                               
        {                                                                      
          if (getenv("GLIBCXX_FORCE_NEW"))                                     
            __atomic_add(&_S_force_new, 1);                                    
          else                                                                 
            __atomic_add(&_S_force_new, -1);                                   
        }                                                                      
                                                                               
          const size_t __bytes = __n * sizeof(_Tp);                            
          if (__bytes > size_t(_S_max_bytes) || _S_force_new == 1)             
        __ret = static_cast<_Tp*>(::operator new(__bytes));                    
          else                                                                 
        {                                                                      
          _Obj* volatile* __free_list = _M_get_free_list(__bytes);             
                                                                               
          lock sentry(_M_get_mutex());                                         
          _Obj* __restrict__ __result = *__free_list;                          
          if (__builtin_expect(__result == 0, 0))                              
            __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes)));        
          else                                                                 
            {                                                                  
              *__free_list = __result->_M_free_list_link;                      
              __ret = reinterpret_cast<_Tp*>(__result);                        
            }                                                                  
          if (__builtin_expect(__ret == 0, 0))                                 
            std::__throw_bad_alloc();                                          
        }                                                                      
        }                                                                      
      else                                                                     
        std::__throw_bad_alloc();                                              
    }                                                                          
      return __ret;                                                            
    }                                                                          
                                                                               
  template<typename _Tp>                                                       
    void                                                                       
    __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n)                  
    {                                                                          
      if (__n)                                                                 
    {                                                                          
      const size_t __bytes = __n * sizeof(_Tp);                                
      if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new == 1)    
        ::operator delete(__p);                                                
      else                                                                     
        {                                                                      
          _Obj* volatile* __free_list = _M_get_free_list(__bytes);             
          _Obj* __q = reinterpret_cast<_Obj*>(__p);                            
                                                                               
          lock sentry(_M_get_mutex());                                         
          __q ->_M_free_list_link = *__free_list;                              
          *__free_list = __q;                                                  
        }                                                                      
    }                                                                          
    }                                                                          
} // namespace __gnu_cxx                                                       
                                                                               
#endif                                                                         